1. Field of the Invention
The present invention relates to an assembled or fabricated piston, consisting partly of ceramic material, for internal or external combustion engines.
2. Description of the Prior Art
Conventionally an engine piston is integrally molded of aluminum material, but lately for the purpose mainly of reducing fuel cost and improving the engine performance there has been an increased need for an assembled piston in which a head facing the combustion chamber and a piston body are constructed as separate pieces, the head being fabricated of a material with good heat insulation such as amber or sintered stainless steel and then being consolidated with the piston body.
In the current practice of manufacturing an assembled piston, the head and the body are bolted together at the center of the piston; or a part of the head made of material other than aluminum is integrally cast into the aluminum body when the body is cast in a mold.
This mode of fastening the head and the body, however, has the drawback that under repeated operation of the engine a difference in the thermal expansion between the head and the body causes repeated stress and deformation variations, resulting in the two parts getting loose, which may lead to engine trouble, trouble in cooling the head, or trouble in sealing.
Moreover, if the head is made of amber or sintered stainless, the piston becomes heavy, resulting in poor performance of the engine.